In oil and gas well drilling operations, drilling fluid is circulated through the drill string, returning formation drill cuttings to the surface through the annulus. The formation drill cuttings are removed from the drilling fluid so that the drill fluid may be reused. A "shale shaker" is typically used for this purpose, which results in drill cuttings accumulating in a trough. The accumulated drill cuttings must be removed from the trough and appropriate disposal must be arranged.
Several methods for removing drill cuttings from the shale shaker trough are known, including various configurations of conveyors, chutes, suction lines, tanks, and other devices. Industry experience has shown that the utilization of a suction line provides several benefits not found in other methods including easier installation, quicker installation, less moving parts, improved safety, lower maintenance, and reduced expense.
Current methods and apparatus utilized in the suction line methods suffer, among other things, from an inability to dispose of the suctioned drill cuttings without interrupting the suction force. This causes substantial delays, and attempts to address this problem have not proven satisfactory.
One known method of utilizing a suction line to remove drill cuttings from the shale shaker trough, involves a tank in which a suction is created, drawing drill cuttings into the tank until full. Once full, however, the suction force must be broken, the suction force connection equipment must be removed from the tank, and the tank must be sealed for removal and replacement by an empty tank. This method in particular has been known to cause substantial delays. Another method involves a single hopper in which a suction force is created, again drawing drill cuttings into the hopper until full. This method also suffers in that the suction force must be terminated in order for the hopper to be opened for discharge of the accumulated drill cuttings.
Known suction line methods also suffer from an inability to properly and efficiently adapt to various methods of disposing of the drill cuttings once they have been removed from the shale shaker trough. For example, although the suction line method utilizing a single hopper can be configured to discharge from the single hopper into a "slurrification unit," the method does not appropriately address the presence of two receiving tanks on most of such slurry units. A slurrification unit typically has two circulating systems, each involving the formulation of a slurry consisting of water and the drill cuttings, with the slurry being circulated, and the cuttings ground to a sufficiently small size for ultimate discharge to an injection pump. The injection pump forces the slurry down the well for reintroduction into porous formations. Any suction line method having only a single hopper discharging into only one slurrification unit tank, fails to take full advantage of the capabilities of the two tank slurrification unit dual circulating systems.
Methods and apparatus are needed which will provide suction line retrieval of drill cuttings from the shale shaker trough, provide continuous suction force in the system, enable efficient post-suction collection and disposal of the drill cuttings, and fully complement the two tank slurrification unit system.